Ultrasonic weld analysis for orthotropic steel decking systems in bridges

Abstract

A system provides for the calculation of the penetration depth of a weld in an orthotropic steel decking system. Weld scan section data is accessed and each scan section along the weld seam is processed to find the amount of penetration as a percentage of the thickness of the rib leg metal at the weld location. The amount of penetration is calculated by finding ultrasonic reflections recorded as voxels that have the greatest magnitude within an area of contiguous magnitudes and then determining the location of those voxels relative to the weld geometry and distance along the thickness of the rib leg steel. A report for each section scan and the entire weld seam may be generated for review by a weld inspector that allows for spot inspections of specified areas along the weld seam for possible weld remediation.

Description

[0001]This application claims the benefit of filing priority under 35 U.S.C. § 119 and 37 C.F.R. § 1.78 of the co-pending U.S. non-provisional application Ser. No. 14 / 986,195 filed Dec. 31, 2015, for a System and Method for the Improved Analysis of Ultrasonic Weld Data. All information disclosed in that prior pending nonprovisional application is hereby incorporated by reference.FIELD OF THE INVENTION[0002]The present invention relates generally to ultrasonic testing of welds. In particular, the present invention relates the ultrasonic testing of welds for orthotropic decking in bridges.BACKGROUND OF THE INVENTION[0003]Modern bridges include separate elements coordinated together to create a strong and durable structure designed to last for many decades or longer. One of those bridge elements is a bridge deck, which provides the support for and the surface upon which man and machine may traverse over whatever the bridge is spanning. In a vehicular bridge, the primary function of the...

AI Technical Summary

Benefits of technology

The present invention provides a system and method for calculating the depth of penetration of a weld in an orthotropic steel decking system. This is done by accessing scan section data for a weld seam and processing it to find the amount of penetration as a percentage of the thickness of the rib leg metal at the weld location. The system can generate a report for each section scan and the entire weld seam for review by a weld inspector that allows for spot inspections of specified areas along the weld seam for possible weld remediation. The technical effect is the improved accuracy and efficiency in weld inspection and quality control in orthotropic steel decking systems.

Problems solved by technology

While well understood and common in bridge building, the use of concrete slabs as a deck presents tremendous weight loads on the primary structures of a bridge, such as the primary cables in a suspension bridge or counter-lever steel beams in a counter levered bridge.

However, the bridge construction industry recognizes that OSD bridges have not been problem-free historically, and they present unique challenges in terms of design and construction as compared to conventional bridge construction.

Fatigue cracking has been observed more frequently in OSD systems resulting from the complicated weld demands combined with stresses that can be more difficult to quantify and, in particular, which were found in early designs which attempted to overly minimize plate thicknesses to reduce weight.

In addition, design loading is determined by live loading (moving vehicles) versus dead loading of the span which requires a precise loading design strategy, and such cyclic live loading dominates the design because fatigue will be the controlling limit for a particular bridge design.

Early analytical tools were limited in their ability to quantify the stress states in these details and the early experimental fatigue resistance database was limited.

Moreover, the fatigue performance of many of these details can be sensitive to fabrication techniques.

Unfortunately, many trials were unsuccessful, and reports of cracking have occurred in re-decking projects where the interactions between new OSD and existing concrete structure were difficult to account for, and created questions among users especially in the United States as to the long-term effectiveness of OSD systems in the highway infrastructure.

The potential for cracking at the rib-to-deck plate weld is indicative of this problem.

Current designs typically are not standardized, and thus repetition does not currently help to improve construction and fabrication techniques, however many welding strategies with respect to rib to deck connection and other OSD elements have been refined over the years to ensure the proper distribution of stress across and to and from the decking.

However, a complication of the closed rib system is in the execution of the one side partial penetration weld for the rib connection to the deck plate.

Also, due to its geometry and inherent torsional strength, closed rib decks are subject to local secondary deformations and stresses that make them vulnerable to fatigue at the intersection at the rib to deck.

Furthermore, field splices of the ribs are also more complicated, and this system requires tolerance control in fabrication and erection to ensure proper fit at the splices.

Generally, partial penetration welds are avoided in bridge design and construction because, depending on the joint configuration, associated stiffness, and the applied stress, such welds can be a fatigue concern.

Further, over years of observation and laboratory testing, welds joining rib legs to the underside of the decking plating are the most common area prone to fatigue cracking due to plate deformation, which is caused by the active loading of vehicles moving over the deck surface.

In addition, testing and experience has shown that a penetration amount of less than 70% provides insufficient weld strength, but a weld penetration amount of greater than 80%, and especially 100%, may lead to fatigue cracking initiated from the weld root when exposed to out-of-plane bending moments.

However, ultrasonic testing is time consuming and conducting more testing than is necessary causes unnecessary delays and cost.

Additionally, while ultrasonic testing is useful for detecting weld defects and various systems are available for such testing, detecting the penetration of a weld using current ultrasonic testing systems is difficult and not optimized to detect the penetration percentage of welds in a rib to deck weld scenario.

In particular, conventional ultrasonic systems (i.e. non-phased array systems) do not have the beam control and resolution to accurately measure the amount of penetration in a weld.

First, probes in conventional ultrasonic systems only offer fixed angles of beam profile, and the beam cannot be focused in a real-time analysis.

So, penetration height cannot be accurately determined in many instances.

Second, conventional ultrasonic systems do not allow a user to focus the beam to provide the necessary resolution to discern certain weld anatomy elements that are required to calculate the penetration of the weld.

In addition, even with phased array ultrasonic systems the time required to do a manual examination of a weld seam along a rib would be impractical.

However, each such manual examination would, if performed by a skilled operator would take 20-30 seconds for each slice.

Hence, even for a relatively short bridge of 1 mile, a manual inspection of weld penetrations on such a bridge even if the number of inspectors was increased would be impractical to the point of never being accomplished in any economically viable manner.

The result is that only imprecise sampling using manual testing is currently done on OSD systems which leaves bridges with mostly untested rib to deck weld seams, the integrity of which is the most fatigue prone element in any bridge construction project.

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